RESUMO
Galanin is a neuropeptide that is widely distributed in the central and peripheral nervous systems. In a previous study, we showed that a small cell lung carcinoma (SCLC) cell line, SBC-3A, released progalanin but not galanin, and that progalanin was then converted to galanin(1-20), the active form. Because the galanin(1-20) had undergone hydrolysis at Arg and Lys residues, the protease concerned was surmised to have a trypsin-like activity. The present study was performed to identify the trypsin-like protease which had previously been found to activate progalanin in this tumor tissue. The protease was isolated using chromatography and electrophoresis, and identified in tumor extracts from SBC-3A tumor-bearing mice; the major protease was found to be plasmin. We next confirmed that extracellular processing of progalanin occurs in SCLC tumor tissue (tumors produced by the implantation of SBC-3A cells into mice), and in two types of breast tumor tissue (obtained by implantation into mice of BT-549 and MDA-MB-436 cells). In cell culture, processed forms of progalanin were undetectable in SBC-3A, BT-549 or MDA-MB-436 cells. Conversely, gel filtration chromatography analysis of tumor extracts from SBC-3A, BT-549 and MDA-MB-436-bearing mice, revealed that galanin-like immunoreactivity (galanin-LI) in these tumor extracts was due to the presence of progalanin (14 kDa) and galanin(1-20) (2 kDa). Moreover, trypsin-like protease activity was elevated, and plasmin was expressed abundantly in SBC-3A, BT-549 and MDA-MB-436 tumors in mice. In addition, tranexamic acid, a plasmin inhibitor, inhibited progalanin conversion to galanin(1-20). The present study revealed that plasmin was present in tumor tissue, and that it was responsible for processing progalanin to galanin(1-20) in the extracellular environment.
Assuntos
Fibrinolisina/metabolismo , Galanina/metabolismo , Animais , Western Blotting , Linhagem Celular Tumoral , Eletroforese em Gel Bidimensional , Fibrinolisina/genética , Galanina/genética , Humanos , Neoplasias Pulmonares/genética , Neoplasias Pulmonares/metabolismo , Camundongos , Radioimunoensaio , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Serina Endopeptidases/genética , Serina Endopeptidases/metabolismo , Carcinoma de Pequenas Células do Pulmão/genética , Carcinoma de Pequenas Células do Pulmão/metabolismoRESUMO
Galanin is a neuropeptide widely distributed in the central and peripheral nervous systems. Although its role in non-neural cells is poorly understood, it is known that during inflammation, the dermis layer of the skin produces and releases galanin. The aim of this report is to study the expression of galanin in granulation tissue. After inducing inflammation by cotton thread implantation, galanin-like immunoreactivity (galanin-LI) in plasma reached a maximum on the third day. Galanin-LI was observed in fibroblast-like cells occurring close to collagen fibers in developing granulation tissue. Furthermore, galanin receptor subtypes 1 and 2 (GALR1 and GALR2)-expressing cells were observed around microvessels and were found to produce desmin. Galanin was injected along the cotton threads immediately after implantation, resulting in rapid formation of granulation tissue, and an increase in the contents of microvessels, indicating a stimulatory effect of galanin on the process of angiogenesis in granulation tissue. The results demonstrate that some galanin was released from fibroblast-like cells during the formation of granulation tissue, and that it stimulated angiogenesis.